April 28, 2013

Zero-Dollar Carbon Fiber Bicycle

Back in January, I was presented with a large carbon fiber tube, in the form of an oar. Being who I am, I made the obvious decision to build a bicycle frame out of it. As I found out when building my bamboo bike, making a bicycle frame from scratch, especially when using composites, is not actually very hard, as long as you have a lot of patience. To make this project more interesting, more challenging, and cheaper, I built the entire frame and bicycle without spending any money on it. Every component (except the pedals, which used to live on the bamboo bike) I either made myself or scavenged.

The frame started its life as a large oar. Apparently it showed up in in a trash pile on a loading dock sometime last year, and found its way to MITERS from there. The carbon fiber tube that made up the shaft of the oar happened to be about the right length and diameter to build the front triangle of a bicycle frame.

I came up with the geometry of the bicycle by shamelessly copying the geometry of the 58cm Trek Madone. Using the lengths and angles provided on their website, I was able to create a fully constrained 2-D SolidWorks sketch of the frame. Using this model, I designed and built a simple frame jig out of 80/20 extrusion and nylon stock.

I have not weighed the entire bike yet, bur from earlier weighings it's probably something like 18 lbs. Not exactly light for a carbon fiber bike, but a good bit lighter than any other bike I've had. The vast majority of the weight is from the components I used. Since I got all the components for free, I did not really have super-light options to choose from.

The bike rides....like a bicycle. Believe it or not, taking 5 pounds or so of a bike does not make a huge difference. Not really surprising, as I make up 85-90% of the mass of the bike-human system. It does make it much more pleasant to carry up and down stairs though. Most of the improvements in this over other bikes I have ridden come from the fit, which is greatly improved over my bamboo bike and my giant steel bike.